A circuit structure of a dual directional coupler

Abstract

The utility model discloses a circuit structure of a dual directional coupler, belonging to the technical field of dual directional couplers, comprising a three-wire strip coupling line, an external compensation circuit 1 and an external compensation circuit 2, wherein the external compensation circuit 1 and the external compensation circuit 2 are respectively connected to one end of two strip coupling lines in the three-wire strip coupling line, the other ends of the two strip coupling lines are respectively connected to resistors 1 and 2, the other ends of the resistors 1 and 2 are connected to the grounding of a PCB board, the external compensation circuit 1 and the external compensation circuit 2 are connected to an isolation port and a coupling port of the PCB board, and the two ends of the third strip coupling line in the three-wire strip coupling line are respectively connected to an input port and an output port of the PCB board. The coupling line is combined with the compensation circuit to achieve high performance indicators (standing wave ratio is less than 1.32, loss is less than 0.3, and power capacity can reach more than 100W), and can meet the flatness requirements of the directional coupler.

Description

Technical Field

[0001] The utility model relates to a circuit structure of a dual directional coupler, belonging to the technical field of dual directional couplers. Background Art

[0002] In modern communication and microwave systems, directional couplers have extremely wide applications and are an important part of microwave circuits. Directional couplers are passive devices that can be designed with any power distribution ratio and are widely used in power detection, power distribution and power synthesis, such as transmitter power control and standing wave protection. In particular, with the development of modern communication and microwave system miniaturization, the performance requirements for directional couplers are becoming higher and higher, and the development is moving towards small size, wide bandwidth, high power, high directivity and other directions.

[0003] Stripline couplers are composed of two or more striplines that are coupled to each other. When two or more center conductor strips are close to each other, the mutual coupling of electric and magnetic field energies forms a coupled stripline coupler.

[0004] The current technologies and technical solutions on the market and their defects and shortcomings:

[0005] Common couplers in the ultra-short wave band mainly include lumped parameter transformer couplers and stripline couplers. Since the saturation magnetization intensity of the ferrite (commonly known as magnetic ring) of the lumped parameter transformer coupler is closely related to temperature, the coupling degree and isolation degree change accordingly. At the same time, the debugging of the lumped parameter transformer coupler is relatively large, the product consistency is poor, and it is not conducive to mass production. At the same time, the lumped parameter transformer coupler cannot meet the high-power design. The stripline coupler just makes up for the above shortcomings, but it is difficult to achieve high performance indicators when the stripline coupler is used directly, and it is also difficult to meet the flatness requirements of the directional coupler. Summary of the invention

[0006] The technical problem to be solved by the utility model is to provide a circuit structure of a dual directional coupler, which can achieve high performance indicators and meet the requirements of flatness of the directional coupler.

[0007] The technical solution adopted by the utility model is: a circuit structure of a dual directional coupler, including a three-wire strip coupling line, an external compensation circuit 1 and an external compensation circuit 2, the external compensation circuit 1 and the external compensation circuit 2 are respectively connected to one end of two strip coupling lines in the three-wire strip coupling line, the other ends of the two strip coupling lines are respectively connected to resistor 1 and resistor 2, the other ends of resistor 1 and resistor 2 are connected to the grounding point of a PCB board, the external compensation circuit 1 and the external compensation circuit 2 are connected to an isolation port and a coupling port of a PCB board, and the two ends of a third strip coupling line in the three-wire strip coupling line are respectively connected to an input port and an output port of the PCB board.

[0008] Furthermore, the above-mentioned external compensation circuit 1 and external compensation circuit 2 both include a resistor R1, an inductor L1, a capacitor C2, a resistor R2, a capacitor C1, an inductor L2, a resistor R3, a capacitor C3 and a resistor R4, one end of the resistor R1 connected in parallel with the inductor L1 is connected to the input end and one end of the capacitor C2, the other end of the resistor R1 connected in parallel with the inductor L1 is connected to one end of the resistor R2 connected in parallel with the capacitor C1, the other end of the resistor R2 connected in parallel with the capacitor C1 is connected to the output end and one end of the capacitor C3, the other end of the capacitor C3 is connected to one end of the resistor R4, the other end of the capacitor C2 is connected to one end of the inductor L2 connected in parallel with the resistor R3, and the other end of the inductor L2 connected in parallel with the resistor R3 is connected to one end of the resistor R4 and the ground end.

[0009] Furthermore, the three-wire strip coupling line is arranged on the upper surface of the lower PCB board and is bent in an arc shape from left to right for multiple times.

[0010] Furthermore, multiple grounding pins are arranged on both sides of the external compensation circuit 1 and the external compensation circuit 2 facing inward, and the multiple grounding pins will be connected to the three-layer grounding terminal of the PCB board.

[0011] Beneficial effects of the utility model: Compared with the prior art, the effects of the utility model are as follows:

[0012] (1) The coupling line is combined with the compensation circuit to achieve high performance indicators (standing wave ratio less than 1.32, loss less than 0.3, power capacity can reach more than 100W), and can meet the flatness requirements of the directional coupler;

[0013] (2) The volume is reduced by using a curved coupling line. The coupling generated by the coupled strip line increases with the frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the overall three-dimensional perspective view of the dual directional coupler;

[0015] Figure 2 is a top view schematic diagram of a three-line strip coupling line arrangement structure;

[0016] Figure 3 It is a schematic diagram of the three-dimensional structure of a dual directional coupler;

[0017] Figure 4 This is a schematic diagram of the three-dimensional structure of the dual directional coupler from another perspective;

[0018] Figure 5 It is a top view structural diagram of a dual directional coupler;

[0019] Figure 6 yes Figure 6 Schematic diagram of the AA section structure;

[0020] Figure 7 This is a schematic diagram of the top view of the lower PCB board;

[0021] Figure 8 It is a schematic diagram of the three-dimensional structure of the upper PCB board;

[0022] Fig. 9 It is a three-line strip coupling line indicator curve graph;

[0023] Fig.10 It is the compensation circuit schematic diagram;

[0024] Fig.11 It is a schematic diagram of the circuit structure of a dual directional coupler;

[0025] Fig.12 It is the compensation circuit index curve diagram;

[0026] Fig.13 is the overall performance graph. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0028] Example 1: Figure 10-11 As shown, the circuit structure of the dual directional coupler includes a three-wire strip coupling line, an external compensation circuit 1 and an external compensation circuit 2, wherein the external compensation circuit 1 and the external compensation circuit 2 are respectively connected to one end of two strip coupling lines in the three-wire strip coupling line 4, the other ends of the two strip coupling lines are respectively connected to resistors 1 and 2, the other ends of resistors 1 and 2 are connected to the grounding of the PCB board 1, the external compensation circuit 1 and the external compensation circuit 2 are connected to the isolation port and the coupling port of the PCB board 1, and the two ends of the third strip coupling line in the three-wire strip coupling line 4 are respectively connected to the input port and the output port of the PCB board. The coupling line is combined with the compensation circuit to achieve high performance indicators, namely, the standing wave ratio is less than 1.32, the loss is less than 0.3, and the power capacity can reach more than 100W, which is unattainable by other process designs. The symmetrical structure realizes dual directional use

[0029] Among them, the external compensation circuit 1 and the external compensation circuit 2 both include a resistor R1, an inductor L1, a capacitor C2, a resistor R2, a capacitor C1, an inductor L2, a resistor R3, a capacitor C3 and a resistor R4, one end of the resistor R1 connected in parallel with the inductor L1 is connected to the input end and one end of the capacitor C2, the other end of the resistor R1 connected in parallel with the inductor L1 is connected to one end of the resistor R2 connected in parallel with the capacitor C1, the other end of the resistor R2 connected in parallel with the capacitor C1 is connected to the output end and one end of the capacitor C3, the other end of the capacitor C3 is connected to one end of the resistor R4, the other end of the capacitor C2 is connected to one end of the inductor L2 connected in parallel with the resistor R3, and the other end of the inductor L2 connected in parallel with the resistor R3 is connected to one end of the resistor R4 and the ground end.

[0030] To achieve adequate grounding and isolation, such as Figure 3 As shown, multiple grounding pins 11 are arranged on both sides of the external compensation circuit 1 and the external compensation circuit 2 facing inward, forming an L-shaped surrounding structure. A row of grounding pins is arranged on the rear side of the external compensation circuit 1 and two rows of grounding pins are arranged on the right side, and a row of grounding pins is arranged on the front side of the external compensation circuit 2 and two rows of grounding pins are arranged on the left side. The multiple grounding pins 11 are arranged at intervals, and the multiple grounding pins are connected to the three-layer grounding terminal of the PCB board 1. On the one hand, sufficient grounding is achieved, and on the other hand, the electromagnetic interference of the supplementary circuit can be isolated to avoid mutual interference between the compensation circuit and the coupling line.

[0031] Example 2: Figure 1-13 As shown, a dual directional coupler comprises a PCB board 1. The PCB board 1 adopts a three-layer structure, including a lower PCB board 2 and an upper PCB board 3 covering the upper surface of the lower PCB board 2. A three-wire strip coupling line 4 with multiple arc bends from left to right is arranged on the upper surface of the lower PCB board 2. An external compensation circuit 1 and an external compensation circuit 2 are arranged at the lower left corner and the upper right corner of the lower PCB board 2 respectively, and a resistor 1 and a resistor 2 are arranged at the upper left corner and the lower right corner. A coupling line groove 5 with the same arc shape as the three-wire strip coupling line 4 is arranged at the bottom of the upper PCB board 3. A first through groove 6, a second through groove 7, a third through groove 8 and a fourth through groove 9 are arranged at the four corners of the upper PCB board 3 respectively. The first through groove 6, the second through groove 7, the third through groove 8 and the fourth through groove 9 are avoidance spaces for the resistor 1, the external compensation circuit 1, the resistor 2 and the external compensation circuit 2 and are filled with glue.

[0032] In order to achieve accurate positioning of the upper and lower boards, the four corners of the lower PCB board 2 and the lower board 2 are positioned by four pairs of positioning pins 10. The four pairs of positioning pins can stably position the four corners to improve installation efficiency and connection stability after installation.

[0033] In order to achieve better compensation, the external compensation circuit 1 and the external compensation circuit 2 use RLC network for compensation.

[0034] In order to improve the performance index of the coupling line, the external compensation circuit 1 and the external compensation circuit 2 are respectively connected to one end of two strip coupling lines in the three-line strip coupling line 4, the other ends of the two strip coupling lines are respectively connected to the resistor 1 and the resistor 2, the other ends of the resistor 1 and the resistor 2 are connected to the grounding point of the PCB board 1, the external compensation circuit 1 and the external compensation circuit 2 are connected to the isolation port and the coupling port of the PCB board 1, and the two ends of the third strip coupling line in the three-line strip coupling line 4 are respectively connected to the input port and the output port of the PCB board. The coupling line is combined with the compensation circuit to achieve high performance indicators, that is, the standing wave ratio is less than 1.32, the loss is less than 0.3, and the power capacity can reach more than 100W, which is unattainable by other process designs.

[0035] Among them, the external compensation circuit 1 and the external compensation circuit 2 both include a resistor R1, an inductor L1, a capacitor C2, a resistor R2, a capacitor C1, an inductor L2, a resistor R3, a capacitor C3 and a resistor R4, one end of the resistor R1 connected in parallel with the inductor L1 is connected to the input end and one end of the capacitor C2, the other end of the resistor R1 connected in parallel with the inductor L1 is connected to one end of the resistor R2 connected in parallel with the capacitor C1, the other end of the resistor R2 connected in parallel with the capacitor C1 is connected to the output end and one end of the capacitor C3, the other end of the capacitor C3 is connected to one end of the resistor R4, the other end of the capacitor C2 is connected to one end of the inductor L2 connected in parallel with the resistor R3, and the other end of the inductor L2 connected in parallel with the resistor R3 is connected to one end of the resistor R4 and the ground end.

[0036] In order to achieve sufficient grounding and isolation, multiple grounding pins 11 are arranged on both sides of the external compensation circuit 1 and the external compensation circuit 2 facing inward, and an L-shaped surrounding structure is formed. A row of grounding pins is arranged on the rear side of the external compensation circuit 1 and two rows of grounding pins are arranged on the right side, and a row of grounding pins is arranged on the front side of the external compensation circuit 2 and two rows of grounding pins are arranged on the left side. The multiple grounding pins 11 are arranged at intervals and connected to the three-layer grounding terminal of the PCB board 1. On the one hand, sufficient grounding is achieved, and on the other hand, the electromagnetic interference of the supplementary circuit can be isolated to avoid mutual interference between the compensation circuit and the coupling line.

[0037] Example 3: Example 2: A dual directional coupler with a compensation circuit and a preparation method thereof, the overall three-dimensional model of the dual directional coupler is as follows Figure 1 As shown in the figure, the dual directional coupler product design adopts a 3-layer PCB board design, using RogersRO4350 board, low loss and good performance. The product consists of a three-wire strip coupling line in the middle, such as Figure 2-8 As shown in the figure, the design uses a curved coupled line to reduce the volume. The coupling generated by the coupled stripline increases with the frequency. The indicators are as follows: Fig. 9 In order to meet the flatness requirements of the directional coupler, a compensation circuit is added to the coupling end to achieve this. The external compensation circuit of the two coupling ends of the three-wire strip coupling line is shown in the schematic diagram. Fig.10 And the connection circuit diagram is as follows Fig.11 , indicators such as Fig.12 (Coupling curve of the compensation circuit). The PCB board adopts a trenching process (four avoidance slots are set at the four corners of the upper PCB board), and the components are embedded in the surface. The PCB board adopts the immersion gold process as a whole, which has the advantages of corrosion resistance and high reliability. In addition, the external compensation circuit is grounded for isolation, and the coupling generated by the designed compensation circuit decreases with increasing frequency. The coupling line is combined with the compensation circuit to achieve high performance indicators (including standing wave ratio, power capacity, insertion loss, etc.; the standing wave ratio is less than 1.2, the loss is less than 0.3, and the power capacity can reach more than 100W, which cannot be achieved by other process designs). In addition, the strip line has a high power resistance, and the selected device adopts 0603 packaging. The product has a power resistance of up to 100W, which far exceeds the performance of the lumped parameter transformer coupler. Product performance indicators Fig.13 (Performance curves of insertion loss, standing wave ratio, coupling and isolation from top to bottom in the figure).

[0038] Furthermore, the above-mentioned external compensation circuit uses an RLC network for compensation.

[0039] Furthermore, the above dual directional coupler has the following specific steps:

[0040] (1) PCB patch

[0041] 1.1 Material preparation:

[0042] Before PCB patch processing, you first need to prepare the required materials, such as circuit boards, electronic components of dual directional couplers, solder paste, flux and other materials. The selection of materials is determined according to the design requirements and production process of the product to ensure the quality and reliability of the materials.

[0043] Component placement:

[0044] The key step of PCB patch processing is to use a high-precision patch machine to accurately mount the electronic components of the dual directional coupler to the corresponding position of the circuit board. The patch machine can achieve fast and accurate patch operation through actions such as suction, movement and placement. The accuracy and position of the patch need to be strictly controlled during the placement process to ensure that the connection between components is correct.

[0045] 1.2 Reflow Oven:

[0046] Reflow soldering is a process in which the circuit board is placed in a reflow soldering oven and, after preheating, soldering and cooling, the solder paste is melted and wets the pins of the electronic components and the pads of the circuit board to form a reliable soldering connection. After the reflow soldering is completed, the PCB board is taken out of the oven, cooled and waits for the soldering to be completed.

[0047] Advantages of PCB patch:

[0048] SMT allows for the use of smaller components, so a higher component density can be achieved on the PCB, making the device more compact. Because the connection distance between components is shortened, signal transmission delays and circuit interference can be reduced. SMT lines can automatically place components at high speed, significantly improving production efficiency and reducing labor costs. Surface mount components generally provide better mechanical stability, especially in terms of vibration and physical shock. SMT is suitable for automated production, reducing human errors and improving product consistency and quality. Less use of copper and other materials is more economical than traditional through-hole soldering (THM).

[0049] (2) Immersion Gold Process

[0050] Process Introduction:

[0051] The immersion gold process is an electrochemical gold plating technology. The immersion gold process deposits a nickel-gold plating layer with stable color, good brightness, flat coating and good solderability on the surface of the printed circuit. It can be basically divided into four stages: pre-treatment (degreasing, micro-etching, activation, post-immersion), nickel immersion, gold immersion, and post-treatment (waste gold washing, DI washing, and drying). It can form a uniform and bright metal film on the surface of the circuit board. This metal film can effectively protect the circuit board from oxidation and corrosion, thereby improving the reliability and durability of the circuit board. In addition, the immersion gold process can also improve the welding performance of the circuit board, making the welding more firm and reliable.

[0052] 2.1 Pre-treatment:

[0053] The pre-treatment of immersion gold generally has the following steps: degreasing, micro-etching, activation, and post-immersion. To remove the oxide on the copper surface of the PCB circuit board, and to precipitate palladium on the copper surface to serve as the activation center for immersion nickel. If any of these links is not handled properly, it will affect the subsequent immersion of nickel and immersion gold, and lead to batch scrapping. During the production process, various potions must be analyzed and supplemented regularly to be controlled within the required range.

[0054] 2.2 Nickel deposition:

[0055] Put the pre-treated PCB into the bath of nickel immersion solution; in the production process, it must be analyzed and tested twice per shift, and Ni reducing agent should be added according to the bare copper area of ​​the PCB. When adding materials, the principle of adding materials in small amounts and dispersed multiple times should be followed, and the temperature of the nickel solution should be controlled at 85℃-90℃;

[0056] The main components of nickel plating solution are Ni, reducing agent sodium hypophosphite and stabilizer. Since chemical nickel has strict requirements on the range of solution components, it must be analyzed and tested twice per shift during the production process, and Ni reducing agent must be added according to the bare copper area of ​​the production board or experience. When adding materials, the principle of small amounts and multiple dispersed additions should be followed to prevent local plating solution from reacting violently and causing accelerated aging of the plating solution. The pH value and plating solution temperature have a greater impact on the nickel thickness. The nickel solution temperature is controlled at 85℃-90℃.

[0057] 2.3 Immersion Gold:

[0058] The pure gold plating layer is replaced on the nickel-phosphorus alloy layer in the bath liquid of the gold-immersion tank of the PCB circuit board after nickel immersion. The pH value of the plating solution is between 4-5, and the temperature is controlled at 85℃-90℃;

[0059] The gold immersion process is a gold immersion process. The main component of the gold immersion tank is Au, and the binder is Ec. It can replace the pure gold plating layer on the nickel-phosphorus alloy layer, making the plating layer smooth and finely crystallized. The pH value of the plating solution is generally between 4-5, and the temperature is controlled at 85℃-90℃

[0060] 2.4 Post-processing:

[0061] Post-processing of printed circuit boards includes: waste gold washing, DI water washing, drying and other steps. You can also use a horizontal board washer to further wash and dry the immersion gold board. The horizontal board washer can be set up in the order of chemical washing (directly mixed sulfuric acid 10% and hydrogen peroxide 30g / L), high-pressure DI water washing, DI water washing, drying, and drying to completely remove the chemical and water stains in the holes and on the surface of the printed circuit board, and obtain an immersion gold board with uniform coating and good brightness.

[0062] Advantages of immersion gold process:

[0063] Immersion gold provides a very flat and solderable surface, promoting better solder joint formation, and the metal gold has excellent oxidation resistance, which can protect the long-term performance of the PCB in harsh environments. The immersion gold layer also has high wear resistance, allowing the PCB to maintain good electrical performance during multiple plug-in and unplug processes. In high-frequency applications, the gold layer can reduce signal loss and improve connection reliability. The gold layer has a certain aesthetics, making the product more visually attractive;

[0064] (3) Lamination: After post-processing, the PCB circuit boards, i.e., the lower PCB board and the upper PCB board, will be laminated with RO4450F prepreg material to obtain a dual directional coupler.

[0065] In summary, in the prepared directional coupler, the coupling line is combined with the compensation circuit to achieve high performance indicators and meet the flatness requirements of the directional coupler.

[0066] The above description is only a specific implementation method of the present utility model, but the protection scope of the present utility model is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present utility model, which should be included in the protection scope of the present utility model. Therefore, the protection scope of the present utility model should be based on the protection scope of the claims.

Claims

1. A circuit structure of a dual directional coupler, characterized in that: The invention comprises a three-wire strip coupling line (4), an external compensation circuit 1 and an external compensation circuit 2, wherein the external compensation circuit 1 and the external compensation circuit 2 are respectively connected to one end of two strip coupling lines in the three-wire strip coupling line (4), the other ends of the two strip coupling lines are respectively connected to a resistor 1 and a resistor 2, the other ends of the resistor 1 and the resistor 2 are connected to the grounding point of a PCB board (1), the external compensation circuit 1 and the external compensation circuit 2 are connected to an isolation port and a coupling port of the PCB board (1), and the two ends of the third strip coupling line in the three-wire strip coupling line (4) are respectively connected to an input port and an output port of the PCB board.

2. The circuit structure of a dual directional coupler according to claim 1, characterized in that: The external compensation circuit 1 and the external compensation circuit 2 both include a resistor R1, an inductor L1, a capacitor C2, a resistor R2, a capacitor C1, an inductor L2, a resistor R3, a capacitor C3 and a resistor R4. One end of the resistor R1 connected in parallel with the inductor L1 is connected to the input end and one end of the capacitor C2. The other end of the resistor R1 connected in parallel with the inductor L1 is connected to one end of the resistor R2 connected in parallel with the capacitor C1. The other end of the resistor R2 connected in parallel with the capacitor C1 is connected to the output end and one end of the capacitor C3. The other end of the capacitor C3 is connected to one end of the resistor R4. The other end of the capacitor C2 is connected to one end of the inductor L2 connected in parallel with the resistor R3. The other end of the inductor L2 connected in parallel with the resistor R3 is connected to one end of the resistor R4 and the ground end.

3. The circuit structure of a dual directional coupler according to claim 1, characterized in that: The three-wire strip coupling line (4) is arranged on the upper surface of the lower PCB board (2) and is bent in an arc shape multiple times from left to right.

4. The circuit structure of a dual directional coupler according to claim 1, characterized in that: A plurality of grounding pins (11) are arranged on both sides of the external compensation circuit 1 and the external compensation circuit 2 facing inwards, and the plurality of grounding pins are connected to the three-layer grounding terminal of the PCB board (1).

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